LET Macro Command

Sets values of substitution variables. Arithmetic and functions are provided.

The general format for this macro command is:

!let <var>=<var1>
!let <var>=<var2><op><var3>
!let <var>=<func1>(<var2>)
!let <var>=<func2>(<var2>,<var3>)
!let <var>=ENV(<str1>[,<var2>])
!let <var>=EVAR(<str1>)
!let <var>=INDX(<str1>,<str2>)
!let <var>=LENG(<str1>)
!let <var>=LWC(<str1>)
!let <var>=SUBS(<str1>,<var1>,[<var2>])
!let <var>=UPC(<str1>)

where:

<var> is a substitution variable.
<var1> is a substitution variable or a constant.
<op> is an arithmetic operator + - omitted, <var1> and <var2> are concatenated as character strings.
<var2> is a numeric substitution variable or a constant.
<var3> is a numeric substitution variable or a constant.
<func1> is a function from the set SQRT, EXP, LOG, LOGE, LOGN, INT, SIN, COS, TAN, ASIN, ACOS, ATAN, ABS.
<func2> is a function from the set MOD, RAIS, MAX, MIN.
<str1> is a string substitution variable or constant.
<str2> is a string substitution variable or constant.
If <str1> or <str2> contain embedded blanks which must be preserved, the variable or constant should be enclosed in (single) quotes.
ENV provides access to environment variables. <str1> is the name of an environment variable. If <var2> is included, it should specify which value (1..N) of the environment variable is required; if omitted, the first value is returned.

EVAR returns a value of 1 if the argument is a valid substitution string, otherwise 0.
INDX returns an integer, representing the starting position within <str1> of a substring identical to <str2>. If <str2> occurs more than once, the position of the first match is returned. If <str2> does not occur within <str1>, INDX returns zero (0).
LENG returns the length of the character string <str1>, (the number of characters up to the first trailing blank).
LWC returns its argument with all upper case letters converted to lower case.
SUBS returns a substring of <str1> that begins at character position <var1> and is at most <var2> characters long. If <var2> is omitted, the remainder of the string is assumed.
UPC returns its argument with all lower case letters converted to their upper case equivalents.

Examples

!let $3=3!let $1=$2
!let $3='$2'
!let $3=$1/$2
!let $5=sin(45)
!let $6=max($1,$3)
!let $d=env(directory)
!let $s=subs($dXXXXX,1,5)
!let $s=$sSUB.DAT

Together, the last three examples will construct the name of the subset file for any directory.