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basic: make variable A the only input variable

Mechanism for assigning inputs to the specified variable is clumsy and uses
binary space. Always using A is much simpler and doesn't seem very limiting to
me. I do that because there's many more "input" commands I'd like to add.
This commit is contained in:
Virgil Dupras 2019-11-24 14:55:50 -05:00
parent e1df320d44
commit 381d57a513
2 changed files with 28 additions and 36 deletions

View File

@ -77,6 +77,16 @@ integer to them. You assign a value to a variable with `=`. For example,
be used in expressions. For example, `print a-6` will print `40`. All variables
are initialized to zero on launch.
### Arguments
Some commands take arguments and there are some common patterns regarding them.
One of them is that all commands that "return" something (`input`, `peek`,
etc.) always to so in variable `A`.
Another is that whenever a number is expected, expressions, including the ones
with variables in it, work fine.
### Commands
There are two types of commands: normal and direct-only. The latter can only
@ -109,26 +119,24 @@ by the next, and so on).
do nothing. For example, `if 2>1 print 12` prints `12` and `if 2<1 print 12`
does nothing. The argument for this command is a "thruth expression".
**input**: Prompts the user for a numerical value and puts that value in the
specified variable. The prompted value is evaluated as an expression and then
stored where specified. For example, `input x` stores the result of the
evaluation in variable `x`. Before the variable name, a quoted string literal
can be specified. In that case, that string will be printed as-is just before
the prompt.
**input**: Prompts the user for a numerical value and puts that value in `A`.
The prompted value is evaluated as an expression and then stored. The command
takes an optional string literal parameter. If present, that string will be
printed before asking for input. Unlike a `print` call, there is no CR/LF after
that print.
**peek/deek**: Put the value at specified memory address into specified
variable. peek is for a single byte, deek is for a word (little endian). For
example, `peek 42 a` puts the byte value contained in memory address 0x002a
into variable `a`. `deek 42 a` does the same as peek, but also puts the value
of 0x002b into `a`'s MSB.
**peek/deek**: Put the value at specified memory address into `A`. peek is for
a single byte, deek is for a word (little endian). For example, `peek 42` puts
the byte value contained in memory address 0x002a into variable `A`. `deek 42`
does the same as peek, but also puts the value of 0x002b into `A`'s MSB.
**poke/doke**: Put the value of specified expression into specified memory
address. For example, `poke 42 0x102+0x40` puts `0x42` in memory address
0x2a (MSB is ignored) and `doke 42 0x102+0x40` does the same as poke, but also
puts `0x01` in memory address 0x2b.
**in**: Same thing as `peek`, but for a I/O port. `in 42 a` generates an input
I/O on port 42 and stores the byte result in `a`.
**in**: Same thing as `peek`, but for a I/O port. `in 42` generates an input
I/O on port 42 and stores the byte result in `A`.
**out**: Same thing as `poke`, but for a I/O port. `out 42 1+2` generates an
output I/O on port 42 with value 3.

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@ -280,15 +280,9 @@ basINPUT:
; If our first arg is a string literal, spit it
call spitQuoted
call rdSep
ld a, (hl)
call varChk
ret nz ; not in variable range
push af ; --> lvl 1. remember var index
call stdioReadLine
call parseExpr
push ix \ pop de
pop af ; <-- lvl 1. restore var index
call varAssign
ld (VAR_TBL), ix
call printcrlf
cp a ; ensure Z
ret
@ -296,9 +290,9 @@ basINPUT:
basPEEK:
call basDEEK
ret nz
ld d, 0
call varAssign
cp a ; ensure Z
; set MSB to 0
xor a ; sets Z
ld (VAR_TBL+1), a
ret
basPOKE:
@ -321,12 +315,7 @@ basDEEK:
; peek address in IX. Let's peek and put result in DE
ld e, (ix)
ld d, (ix+1)
call rdSep
ld a, (hl)
call varChk
ret nz ; not in variable range
; All good assign
call varAssign
ld (VAR_TBL), de
cp a ; ensure Z
ret
@ -356,13 +345,8 @@ basIN:
push ix \ pop bc
ld d, 0
in e, (c)
call rdSep
ld a, (hl)
call varChk
ret nz ; not in variable range
; All good assign
call varAssign
cp a ; ensure Z
ld (VAR_TBL), de
; Z set from rdExpr
ret
basSLEEP: