The BBC and Master Computer Public Domain Library

904A LET

Submitted by Steve Fewell

Description:

Call routine &98AE to evaluate the variable name - check whether it exists or not
and create the variable if it does not exist. &98AE also returns with &2A and &2B pointing
to the address of the variable's value (which will be blank (zero) if the variable was newly created),
and &2C set to the variable's type.

If the zero flag is set, then there was an error and the text after the LET command
was not a valid variable name, so issue a Syntax Error.

If the Carry flag is clear then the variable has a numerical value type (E.g. Integer or Floating-Point),
so do the following:
* Store &2A, &2B and &2C on the stack (to save variable info for the Set numerical variable
routine (&B32B) to retrieve)
* Call routine &9B52 to check for '=' (if no '=' then Mistake error), get result of expression and check
that the Statement Line is terminated correctly (if it isn't then Syntax Error).
* Call routine &B32B to set the numerical variable to the value of the expression, or issue
Type mismatch error if the expression returned a String value.
* Jump to routine &9005 to continue running the BASIC program/command line.

If the Carry flag is set then the variable has a String value type, so do the following:

* Push the IWA (&2A-&2D) to the BASIC stack (to save variable info for the Set String variable
routine (&90AB) to retrieve)
* Call routine &9B52 to check for '=' (if no '=' then Mistake error), get result of expression and check
that the Statement Line is terminated correctly (if it isn't then Syntax Error).
* Issue a Type mismatch error if the expression returned a numerical (non string) value.
* Call routine &90AB to set the String variable to the value of the expression.
* Jump to routine &9005 to continue running the BASIC program/command line.

Disassembly for the LET routine