diff options
Diffstat (limited to 'txr.1')
| -rw-r--r-- | txr.1 | 22 |
1 files changed, 21 insertions, 1 deletions
@@ -13675,6 +13675,8 @@ In this situation, if the call does not specify a value for the parameter (colon)) then the parameter takes on the value of the expression .metn expr . +This expression is only evaluated when its value is required. + If .meta sym is specified, then @@ -13683,7 +13685,9 @@ will be introduced as an additional binding with a Boolean value which indicates whether or not the optional parameter had been specified by the caller. -The initializer expressions are evaluated an environment in which +Each +.code expr +that is evaluated is evaluated an environment in which all of the previous parameters are visible, in addition to the surrounding environment of the lambda. For instance: @@ -13707,6 +13711,22 @@ by the surrounding let. This reference is captured as part of the .codn lambda 's lexical closure. +Keyword symbols, and the symbols +.code t +and +.code nil +may not be used as parameter names. +The behavior is unspecified if the same symbol is specified +more than once anywhere in the parameter list, whether as a parameter name or as +the indicator +.code sym +in an optional parameter or any combination. + +Implementation note: the \*(TX compiler diagnoses and rejects duplicate +symbols in +.code lambda +whereas the interpreter ignores the situation. + .TP* Examples: .IP "Counting function:" This function, which takes no arguments, captures the |