diff options
Diffstat (limited to 'txr.1')
| -rw-r--r-- | txr.1 | 48 |
1 files changed, 48 insertions, 0 deletions
@@ -14384,6 +14384,19 @@ value into and returns .codn t . +.meIP (ensure < place << init-expr ) +If the place is +.codn nil , +evaluates +.codn init-expr , +stores that value into +.meta place +and returns it. +Otherwise, returns the value of +.meta place +without changing its value or evaluating +.codn init-expr . + .meIP (inc < place <> [ delta ]) Increments .meta place @@ -42858,6 +42871,41 @@ expression, stores the resulting value into and returns .codn t . +.coNP Macro @ ensure +.synb +.mets (ensure < place << init-expr ) +.syne +.desc +The +.code ensure +macro examines the value of +.metn place . + +If the current value is +.codn nil , +then +.meta init-expr +is evaluated. The value is stored in +.meta place +and becomes the result of the +.code ensure +form. + +If the value of +.meta place +is other than +.codn nil , +then the form yields that value. +In this case, +.meta init-expr +isn't evaluated, and +.meta place +isn't modified. + +The +.meta place +expression is evaluated only once to determine the place. + .coNP Macros @ inc and @ dec .synb .mets (inc < place <> [ delta ]) |