Value   built-in function

The Value function returns the value of a symbol, and optionally assigns the name a new value. Normally, symbols are accessed within the current procedure scope; including exposed symbols. Alternatively, the Value function accesses symbols in external pools.

You can often use the Value function instead of the Interpret instruction.

result = Value( symbol [, [ newvalue ] [, pool ] ] )

symbol

the name of the symbol to access. This must be a valid symbol name. If you are unsure whether a valid symbol name is being passed as an argument, you should check its validity with the Symbol function beforehand.

newvalue

an optional value to assign to the symbol.

pool

an optional name of an external pool. When this argument is absent, the symbol is accessed in the current procedure's symbol scope.

Please observe:

1. When the pool argument is specified, the symbol argument does NOT have to be a valid symbol name. In this circumstance, the interpretation of the symbol argument is implementation-dependent. The variable pool is accessible throughout all Rexx procedure levels; including external procedures. Consequently, a pool is a collection of external global variables. The value of variables in a pool may persist after the current Rexx process concludes. The behavior of a symbol pool is implementation-dependent.

2. The NOVALUE condition is never raised, even if the referenced symbol value is uninitialized. The default value of the variable is returned if the symbol is unassigned. This can lead to unexpected program behavior -- particularly if you thought references to unassigned variables would raise the NOVALUE condition.

3. Characters within the symbol name are converted to upper case, AND THEN substitution in a compound name will occur if possible. This can cause an unexpected surprise if the value of part of a compound name contains lower case letters. In the following example, part of a compound name's value is 'this'.

   v = 'this' symbol.v = 'that' -- SYMBOL.this = that .. but SYMBOL.THIS is undefined say symbol.v -- shows: that say value( 'SYMBOL.'v ) -- shows: SYMBOL.THIS [expected: that]

   Contrast the above with the following, where the part of a compound name's value is 'THIS'.

   v = 'THIS' symbol.v = 'that' -- SYMBOL.THIS = that say symbol.v -- shows: that say value( 'SYMBOL.'v ) -- shows: that

Examples: /* the following instructions establish the context for the value function calls */ drop a3 a33 = 7 k = 3 fred='K' list.5 = '?' /* now study the results of the value function calls */ say Value( 'a'k ) -- shows: A3 .. an unassigned symbol say Value( 'a'k || k ) -- shows: 7 .. the value of symbol a33 say Value( 'fred' ) -- shows: K .. the value of symbol FRED say Value( fred ) -- shows: 3 .. the value of symbol K say Value( fred, 4 ) -- shows: 3 .. then assigns K the value 4 call Value fred, 5 -- assigns K the value 5 say Value( fred ) -- shows: 5 .. shows that indeed K was assigned the value 5 say Value( 'LIST.'k ) -- shows: ? .. the value of list.5 /* this shows how to prevent an invalid call to the Value function */ char = '>' if symbol( char ) = 'BAD' then   say char 'is not a valid symbol name' else   say value( char ) /* external pool value function requests */ say Value( 'Destination', 'Vienna', 'Vacation' )'_' -- shows: _ .. prior destination is empty, and assigns new destination say Value( 'Destination', 'Belgrade', 'Vacation' ) -- shows: Vienna .. prior destination, and assigns new destination call Value 'Destination', 'Nice', 'Vacation' -- assigns new destination say Value( 'Destination', , 'Vacation' ) -- shows: Nice