REPL Capabilities

REPL (Read-Eval-Print Loop) is the Dino-GSP canvas’s interactive command interface, providing full control over the canvas for AI and developers. Execute single commands via the SDK’s repl method; output is in AI-oriented document/text format (tables, structured text) for easy parsing and decision-making.

Integration

const sdk = await AlgeoSdk.create(container);
const { output } = await sdk.repl('help');
const { output } = await sdk.repl('list');
const { output } = await sdk.repl('def A := Point(0,0)');

Each call executes a single command. On error, the promise rejects; see Protocol - Error Codes.

Command Categories

Slide Management

Command	Description
list_slides	List all slides (index, ID, definition count)
new_slide [idx]	Create new slide, optionally at position
switch_slide <idOrIdx>	Switch to specified slide
dup_slide <idOrIdx> [tgtIdx]	Duplicate slide
move_slide <idOrIdx> <tgtIdx>	Move slide order
del_slide <idOrIdx>	Delete slide

idOrIdx: use index (1-based) or ID (e.g. slide_abc123).

Definition Management

Command	Description
list	List all definitions on current slide (ID, type, value, definition, label, visibility, etc.)
def <ID> := <Expr>	Define or modify geometry element
def <ID> : <Type> := <Expr>	Definition with type annotation
def <ID>.label := <Expr>	Define/modify element label
label <ID> := <Expr>	Same as above
undef <ID1> <ID2> ...	Remove one or more definitions
rename <OldID> to <NewID>	Rename element
clear	Clear current slide
eval <Expr>	Evaluate expression for computation/verification

Point Selection and Intersection on Objects

Command	Description
snap_point [<ID> :=] <Obj> near (<X>,<Y>)	Select point on object nearest to (X,Y)
intersect [<ID> :=] <ObjA> with <ObjB> near (<X>,<Y>)	Define intersection of two objects nearest to (X,Y)

Supported objects: Line, Circle, Segment, Ray, Arc, Ellipse, EllipticArc, Curve, etc.

Style Management

Command	Description
check_style <Selector>	View style for given selector
style <SelectorList> { <Property>:<Value>; ... }	Set style
unset_style <SelectorList>	Clear style

Selectors: Background, XAxis, YAxis, Grid, #<ID>, <Type>:label, #<ID>:label.

Help

Command	Description
help	Default help
help <Topic>	Query by topic (commands, types, syntax, globals, transform, etc.)

Geometry Types and Constructions

Points

• Point(x, y): Fixed point
• Point(?:=x, ?:=y): Draggable point
• MidPoint(A, B): Midpoint

Lines

• Line(P1, P2), Segment(P1, P2), Ray(Start, Through)
• PerpLine(Line, Point), ParallelLine(Line, Point), PerpBisector(Segment)
• Tangent(CircleOrArc, Point), AngleBisector<Angle>

Circles and Arcs

• Circle(Center, Radius) / Circle(Center, Point)
• Circumcircle(P1, P2, P3), Arc(...), SemiCircle(P1, P2)

Polygons

• Polygon(...Points), Polygon(A, B, NumEdges), Parallelogram(P1, P2, P3)

Curves

• Explicit: Curve(y=x²)
• Parametric: Curve(x(t), y(t), start, end)
• Implicit: Curve(f(x,y)=0)

Transformations

• Translate(Obj, Point), Rotate(Obj, Angle, Center), Reflect(Obj, Line), Scale(Obj, Factor, Center)

Intersections

• Intersect(A, B, Index): Intersection of elementary geometry objects; Index is 1-based
• eval Intersect(A, B): List all intersections

Labels and Text

• def <ID> := "<string>": Text object
• Label templates: "", "", "", "", etc.
• Supports for expression references

Output Format

• Tables: list, list_slides, check_style, etc. output in table form
• Single line: def, eval, style, etc. return a single line or brief description
• Help: help returns Markdown text

Example list columns: ID, type, value, definition, label, visibility, whether sub-object.

Syntax and Constraints

• Comments: -- for single-line comments
• Identifiers: Start with letter, may include digits and underscores
• Coordinates: 1 unit ≈ 50px; recommended range ±10
• Geometry constraints: Prefer geometric constructions over coordinate approximations

Quick Examples

-- Query help
help
help Point
help Curve

-- Slide operations
list_slides
new_slide
switch_slide 1

-- Define geometry objects
def A := Point(0,0)
def B := Point(1,0)
def l := Line(A,B)
def c := Circle(A, 2)

-- Intersection
def P := Intersect(l, c, 1)

-- Labels
label A := "{{id}}"

-- Styles
style XAxis, YAxis { show: true; }
style #A { color: #FF0000; pointSize: 7; }

-- Query and verify
list
eval A.x + B.x