Text I/O and Hashing

numeric hash value of a string

write string to file

read string from file

Conditional Expression Evaluation

SMath workbook must be saved before proceeding

Let's say we would like to evaluate simple expression c:=a+b only if either a or b changed. In order to do that, every time expression is evaluated, a log entry will be created with its Expression ID (say ID#1), hash of the input (say a*b) and resulting output c:+a+b

log_OUT function tries to read log entry that starts with ID#1, does not find it and suggests that expression must be recalculated and log entry saved.

log_IN fuction converts input a+b to hash code, and writes a log entry similar to: "ID#1"-#BREAK#-HASHCODE-#BREAK#-EXPRESSIONOUTPUT

Now log_OUT function can pick up stored output instead of evaluating c:=a+b.

I will clear the log file so the cycle can be repeated

Condensed if() Loop for Conditional Expression Evaluation

If() loop below will ONLY evaluate if it cannot find logged function output for a given expression ID and input value