EVAL Keyword

EVAL string-expression
````
 
Executes BASIC code supplied in `string-expression`.
 
* If the string contains a **single line**, it is executed in the **current program's context**.
* If the string contains **multiple lines**, it is executed as an **anonymous child program** in a new process context.
 
On **error**, `ERR$` is set to the error message and `ERR` is set to `1`. Execution then continues at the statement after `EVAL`.
 
* Recursive **single-line EVAL** is not permitted.
 
\remark If you need a literal double quote inside the evaluated line, insert it using `CHR$(34)`.
\remark For example: `EVAL "PRINT " + CHR$(34) + "Hello" + CHR$(34)`.
 
---
 
### Examples
 
**Print from a generated line (single-line)**

basic EVAL "PRINT " + CHR$(34) + "Hello from EVAL!" + CHR$(34)

**Set a variable dynamically**

basic NAME$ = "COUNT" EVAL NAME$ + " = 42" PRINT COUNT

**Call a procedure**

basic DEF PROCgreet PRINT "Greetings" ENDPROC

EVAL "PROCgreet"

**Multi-line anonymous program**

basic EVAL "A=1" + CHR$(10) + "PRINT A"

**Using GLOBAL variables in multi-line EVAL**

basic GLOBAL A A = 5

EVAL "PRINT A"

**Error handling (ERR/ERR$ set, program continues)**

basic ERR = 0 ERR$ = ""

EVAL "A = 1/0"

IF ERR <> 0 THEN PRINT "EVAL failed: "; ERR$ ENDIF ```

---

Notes

• A single-line EVAL executes in the current context and has access to all variables, procedures, and functions.
• A multi-line EVAL runs as an anonymous child program.
• Anonymous child programs inherit GLOBAL variables from the parent.
• Single-line EVAL executes via a temporary injected line; therefore, recursive single-line EVAL is not permitted.
• Provide exactly one statement when using single-line EVAL; statement separators are not supported.
• Use EVAL for dynamic or generated code. For larger logic, prefer normal procedures or separate programs.

See also: DEF, PROC, FN, ERR, ERR$