1 | ;;;; shift-reset.scm |
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2 | ;;;; Kon Lovett, Apr 6 '06 |
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3 | |
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4 | ;; Dynamically scoped shift/reset (Olivier Danvy & Andrzej Filinski) |
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5 | |
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6 | (module shift-reset (;export |
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7 | ;; |
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8 | ;(%reset *%reset) (%shift *%shift) |
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9 | (reset *reset) (shift *shift) |
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10 | ;(%reset-values *%reset-values) (%shift-values *%shift-values) |
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11 | (reset-values *reset-values) (shift-values *shift-values) |
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12 | ;; |
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13 | ;*%reset *%shift |
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14 | *reset *shift |
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15 | ;*%reset-values *%shift-values |
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16 | *reset-values *shift-values) |
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17 | |
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18 | (import scheme |
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19 | (except chicken reset) |
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20 | (only miscmacros let/cc)) |
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21 | |
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22 | (require-library miscmacros) |
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23 | |
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24 | (declare |
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25 | (always-bound |
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26 | *meta-dk* |
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27 | *meta-k* |
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28 | *meta-dkv* |
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29 | *meta-kv*)) |
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30 | |
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31 | #; ;REMOVED |
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32 | (define-syntax %reset |
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33 | (syntax-rules () |
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34 | ((_ BODY ...) (*%reset (lambda () BODY ...)) ) ) ) |
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35 | |
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36 | #; ;REMOVED |
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37 | (define-syntax %shift |
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38 | (syntax-rules () |
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39 | ((_ SP BODY ...) (*%shift (lambda (SP) BODY ...)) ) ) ) |
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40 | |
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41 | (define-syntax reset |
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42 | (syntax-rules () |
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43 | ((_ BODY ...) (*reset (lambda () BODY ...)) ) ) ) |
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44 | |
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45 | (define-syntax shift |
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46 | (syntax-rules () |
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47 | ((_ SP BODY ...) (*shift (lambda (SP) BODY ...)) ) ) ) |
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48 | |
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49 | #; ;REMOVED |
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50 | (define-syntax %reset-values |
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51 | (syntax-rules () |
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52 | ((_ BODY ...) (*%reset-values (lambda () BODY ...)) ) ) ) |
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53 | |
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54 | #; ;REMOVED |
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55 | (define-syntax %shift-values |
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56 | (syntax-rules () |
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57 | ((_ SP BODY ...) (*%shift-values (lambda (SP) BODY ...)) ) ) ) |
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58 | |
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59 | (define-syntax reset-values |
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60 | (syntax-rules () |
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61 | ((_ BODY ...) (*reset-values (lambda () BODY ...)) ) ) ) |
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62 | |
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63 | (define-syntax shift-values |
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64 | (syntax-rules () |
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65 | ((_ SP BODY ...) (*shift-values (lambda (SP) BODY ...)) ) ) ) |
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66 | |
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67 | ;; |
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68 | ;; Local impl of continuation binding |
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69 | ;; |
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70 | |
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71 | #; ;REMOVED |
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72 | (define-syntax let/scc |
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73 | (syntax-rules () |
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74 | ((_ K BODY ...) (##sys#call-with-current-continuation (lambda (K) BODY ...)) ) ) ) |
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75 | |
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76 | #; ;REMOVED |
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77 | (define-syntax let/cdc |
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78 | (syntax-rules () |
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79 | ((_ K BODY ...) (##sys#call-with-direct-continuation (lambda (K) BODY ...)) ) ) ) |
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80 | |
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81 | (define-syntax let/ccp |
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82 | (syntax-rules () |
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83 | ((_ K BODY ...) (continuation-capture (lambda (K) BODY ...)) ) ) ) |
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84 | |
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85 | ;; |
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86 | ;; Common error |
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87 | ;; |
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88 | |
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89 | (define (bad-k s r) (error s "no toplevel in scope" r)) |
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90 | |
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91 | ;; |
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92 | ;; Single Valued - Without Dynamic-Wind |
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93 | ;; |
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94 | |
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95 | #; ;REMOVED |
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96 | (define *meta-dk* (lambda (val) (bad-k '%shift '%reset))) |
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97 | |
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98 | #; ;REMOVED |
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99 | (define (*%return EXPR) (##sys#direct-return *meta-dk* EXPR)) |
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100 | |
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101 | #; ;REMOVED |
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102 | (define (*%reset thunk) |
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103 | (let ((meta-dk *meta-dk*)) |
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104 | (let ((val (let/cdc k |
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105 | (set! *meta-dk* k) |
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106 | (*%return (thunk))))) |
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107 | (set! *meta-dk* meta-dk) |
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108 | val) ) ) |
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109 | |
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110 | #; ;REMOVED |
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111 | (define (*%shift proc) |
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112 | (let/cdc k |
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113 | (*%return |
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114 | (proc |
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115 | (lambda (val) |
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116 | (*%reset |
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117 | (lambda () |
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118 | (##sys#direct-return k val)))))) ) ) |
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119 | |
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120 | ;; |
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121 | ;; Single Valued - With Dynamic-Wind |
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122 | ;; |
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123 | |
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124 | (define *meta-k* (lambda (val) (bad-k 'shift 'reset))) |
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125 | |
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126 | (define-syntax *return |
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127 | (syntax-rules () |
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128 | ((_ EXPR) (*meta-k* EXPR)) ) ) |
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129 | |
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130 | (define (*reset thunk) |
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131 | (let ((meta-k *meta-k*)) |
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132 | (let/cc k |
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133 | (set! *meta-k* |
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134 | (lambda (val) |
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135 | (set! *meta-k* meta-k) |
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136 | (k val))) |
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137 | (*return (thunk)) ) ) ) |
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138 | |
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139 | (define (*shift proc) |
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140 | (let/cc k |
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141 | (*return (proc (lambda (val) (*reset (lambda () (k val)))))) ) ) |
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142 | |
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143 | ;; |
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144 | ;; Multi-Valued - Without Dynamic-Wind |
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145 | ;; |
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146 | |
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147 | #; ;REMOVED |
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148 | (define *meta-dkv* (lambda vals (bad-k '%shift-values '%reset-values))) |
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149 | |
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150 | #; ;REMOVED |
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151 | (define-syntax *%return-values |
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152 | (syntax-rules () |
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153 | ((_ EXPR) |
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154 | (call-with-values |
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155 | (lambda () EXPR) |
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156 | (lambda vals (apply *meta-dkv* vals))) ) ) ) |
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157 | |
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158 | #; ;REMOVED |
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159 | (define (*%reset-values thunk) |
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160 | (let ((meta-dkv *meta-dkv*)) |
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161 | (call-with-values |
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162 | (lambda () |
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163 | (let/scc k |
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164 | (set! *meta-dkv* k) |
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165 | (*%return-values (thunk)))) |
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166 | (lambda vals |
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167 | (set! *meta-dkv* meta-dkv) |
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168 | (apply values vals))) ) ) |
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169 | |
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170 | #; ;REMOVED |
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171 | (define (*%shift-values proc) |
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172 | (let/scc k |
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173 | (*%return-values (proc (lambda vals (*%reset-values (lambda () (apply k vals)))))) ) ) |
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174 | |
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175 | ;; |
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176 | ;; Multi-Valued - With Dynamic-Wind |
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177 | ;; |
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178 | |
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179 | (define *meta-kv* (void)) |
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180 | |
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181 | (define-syntax *return-values |
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182 | (syntax-rules () |
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183 | ((_ EXPR CALLER) |
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184 | (if (continuation? *meta-kv*) (continuation-graft *meta-kv* (lambda () EXPR)) |
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185 | (bad-k CALLER 'reset-values) ) ) ) ) |
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186 | |
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187 | (define (*reset-values thunk) |
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188 | (let ((meta-kv *meta-kv*)) |
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189 | (call-with-values |
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190 | (lambda () |
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191 | (let/ccp k |
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192 | (set! *meta-kv* k) |
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193 | (call-with-values |
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194 | thunk |
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195 | (lambda vals |
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196 | (*return-values (apply values vals) 'reset-values))))) |
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197 | (lambda vals |
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198 | (set! *meta-kv* meta-kv) |
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199 | (apply values vals))) ) ) |
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200 | |
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201 | (define (*shift-values proc) |
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202 | (let/ccp k |
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203 | (*return-values |
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204 | (proc (lambda vals (*reset-values (lambda () (apply continuation-return k vals))))) |
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205 | 'shift-values) ) ) |
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206 | |
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207 | ) ;module shift-reset |
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